CN108809521B - Variable length decoding method and device and variable length decoder - Google Patents

Variable length decoding method and device and variable length decoder Download PDF

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CN108809521B
CN108809521B CN201810672004.2A CN201810672004A CN108809521B CN 108809521 B CN108809521 B CN 108809521B CN 201810672004 A CN201810672004 A CN 201810672004A CN 108809521 B CN108809521 B CN 108809521B
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CN108809521A (en
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韩赛
马红兵
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China United Network Communications Group Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0014—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the source coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
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Abstract

The embodiment of the invention provides a variable length decoding method, a variable length decoding device and a variable length decoder, relates to the technical field of communication, and solves the problem that in the prior art, when transmission parameters simultaneously relate to absolute values and symbols to be respectively coded, and when a transmission channel has noise interference, the variable length decoder cannot correctly identify the position of a code word corresponding to each transmission character in a bit stream, and different codebooks corresponding to the absolute values and the symbols are added, so that an information source signal cannot be correctly recovered. The method comprises determining a first boundary time l of a divergent phase and a fixed phase in the lattice structuredsSecond boundary time l of the fixed phase and the merging phasesc(ii) a And determining the information transmitted at the ith transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value code word in the ith transmission moment absolute value codebook and the symbol posterior probability of each symbol code word in the ith transmission moment symbol codebook. The embodiment of the invention is used for manufacturing the variable length decoder.

Description

Variable length decoding method and device and variable length decoder
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a variable length decoding method and apparatus, and a variable length decoder.
Background
As shown in fig. 1, in digital communication, in order to better transmit characters in a channel, a source encoder converts a source signal into a bit stream according to a preset encoding rule, then transmits the bit stream to a source decoder through the channel, and then the source decoder converts and restores the bit stream into original information according to a preset decoding rule, wherein the encoding rule corresponds to the decoding rule one to one; to achieve better compression during transmission, variable-length codes (VLCs) may be used to map each quantized source character into a different number of bit combinations. Because of their good compression performance, VLCs are widely used in communications in image, video, and audio codecs, such as high-performance advanced audio encoders HE-AAC, which are widely used in wireless streaming media. In the case of transmission error-free, the VLCs decoder can correctly identify the beginning and ending positions of the corresponding codeword in the bitstream for each character, but cannot correctly identify it in the case of error-prone channels, causing severe distortion. And once there is an error, the error is accumulated all the time. There is therefore a need for a robust decoder for VLCs.
Some current researches are to improve robustness by combining some soft information with a soft decision decoding method by means of trellis representation. The advantage of the trellis representation is that it takes into account the total number of possible transmission bits for a certain transmission moment. In the conventional trellis representation, characters at all time instants are encoded based on the same codebook, and for some parameters, absolute values and signs of the characters are transmitted respectively (such as parameters of quantized spectral coefficients in high-performance advanced audio coding HE-AAC), the absolute values and signs are encoded based on different variable length coding codebooks, so that in order to improve the robustness of the quantized spectral coefficients similar to those in HE-AAC by using a soft-decision decoding method, a decoder based on a novel trellis representation is required to recover the source signal more accurately.
It can be seen from the above description that, in the prior art, when the transmission parameters relate to absolute values and symbols for encoding respectively, and when a transmission channel has noise interference, since the variable length decoder cannot correctly identify the position of the codeword corresponding to each transmission character in the bit stream, and in addition, the absolute values and symbols correspond to different codebooks, how to correctly recover the source signal more accurately becomes an urgent problem to be solved.
Disclosure of Invention
The embodiment of the invention provides a variable length decoding method, a variable length decoding device and a variable length decoder, which solve the problem that in the prior art, when transmission parameters relate to absolute values and symbols to be respectively coded and a transmission channel has noise interference, the variable length decoder cannot correctly identify the position of a code word corresponding to each transmission character in a bit stream, and different codebooks are corresponding to the absolute values and the symbols, so that an information source signal cannot be correctly recovered.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
first aspect, practice of the inventionAn embodiment provides a variable length decoding method, including: acquiring the total number B and the total bit number R of characters transmitted in a bit stream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0; according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by the symbol code word in the symbol codebook, the total number B of characters and the total bit number R are determined, and the first boundary time l of a divergent stage and a fixed stage in the lattice structure is determineddsSecond boundary time l of the fixed phase and the merging phasesc(ii) a According to the first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set of the first transmission time is VstartThe maximum value of the first set of the ith transmission time is VendAnd the minimum value of the second set of the l transmission time instants is V'startThe maximum value of the second set of the l transmission time instants is V'end(ii) a The first set comprises at least one possible state, the state in the first set refers to the total number of bits of which the absolute value is transmitted to the current transmission time, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of which the symbols are transmitted to the current transmission time, the total number of the states in the first set corresponding to each transmission time in the divergence phase is in an increasing trend, the total number of the states in the first set corresponding to each transmission time in the fixed phase is kept unchanged, and the total number of the states in the first set corresponding to each transmission time in the combination phase is gradually reduced until the known total number of characters B and bits R are reached, and the divergence phase, the fixed phase or the combination phase is achievedPhases are differentiated for absolute values only; acquiring prior probability and bit error probability; v of a first set transmitted per transmission instant according to a codebook of absolute valuesstartV of the first setendDetermining the posterior probability of the absolute value of each absolute value code word in the absolute value codebook at each transmission moment; v 'of a second set transmitted per transmission time instant according to a codebook of symbols'startV 'of the second set'endDetermining the symbol posterior probability of each symbol code word in the symbol codebook at each transmission moment; and determining the information transmitted at the ith transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the ith transmission moment absolute value codebook and the symbol posterior probability of each symbol in the ith transmission moment symbol codebook.
Optionally, the minimum bit number N occupied by the absolute value codeword in the absolute value codebook is usedminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by the symbol code word in the symbol codebook, the total number B of characters and the total bit number R are determined, and the first boundary time l of a divergent stage and a fixed stage in the lattice structure is determineddsSecond boundary time l of the fixed phase and the merging phasescThe method comprises the following steps: according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number N 'of code words actually used by absolute values in the trellis structure according to the minimum bit number x and the maximum bit number t occupied by symbol code words in the symbol codebook, the total number B of characters and the total bit number R'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure BDA0001708568250000031
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure BDA0001708568250000032
r' from
Figure BDA0001708568250000033
Starting, continuously adding 1, and stopping adding 1 when R' meets the variable formula;
according to the determined minimum bit number N'minN 'maximum number of bits'maxIntermediate variable R 'and intermediate variable l', determining second boundary time l of fixed stage and merging stage in lattice structurescAnd a maximum value q of the total number of states contained in the first setmax(ii) a According to qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, according to the determined minimum bit number N'minN 'maximum number of bits'maxIntermediate variables R 'and l' to determine the second boundary time l of the fixed phase and the merging phasescAnd a maximum value q of the total number of states contained in the first setmaxThe method comprises the following steps:
when it is determined that R is not more than Nmin× B + t, second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
When it is determined that R is not more than Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), second boundary time lscIs equal to
Figure BDA0001708568250000041
Maximum value qmaxIs equal to R-N'min×B+1；
When it is determined that R < R', a second boundary time lscIs equal to
Figure BDA0001708568250000042
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
When it is determined that R < Nmax× B + t × (B-1), second boundary time lscIs equal to
Figure BDA0001708568250000043
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
When it is determined that R.gtoreq.Nmax× B + t × (B-1), second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
According to qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+ t, comprising:
according to the maximum value qmaxDetermining a first boundary instant ldsIs equal to
Figure BDA0001708568250000044
The maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, according to the first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission time and a second set of states corresponding to the symbols, including:
when it is determined that the transmission time/is less than or equal to the first boundary time/dsWhile determining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
When it is determined that the transmission time/is greater than the first boundary time/dsAnd the transmission time l is less than or equal to the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
When it is determined that the transmission time l is greater than the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
A second aspect of an embodiment of the present invention provides a variable length decoding apparatus, including: the acquisition module is used for acquiring the total number B and the total bit number R of the characters transmitted in the bit stream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0; a processing module for calculating the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxDetermining a minimum bit number x and a maximum bit number t occupied by a symbol codeword in a symbol codebook, a total number B of characters acquired by an acquisition module and a total bit number R acquired by the acquisition module, and determining a first boundary time l of a divergent stage and a fixed stage in a lattice structuredsSecond boundary time l of the fixed phase and the merging phasesc(ii) a A processing module, further used for determining a first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set of the first transmission time is VstartThe maximum value of the first set of the ith transmission time is VendAnd the minimum value of the second set of the l transmission time instants is V'startThe maximum value of the second set of the l transmission time instants is V'end(ii) a The first set comprises at least one possible state, the state in the first set refers to the total number of bits of which the absolute value is transmitted to the current transmission time, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of which the symbols are transmitted to the current transmission time, the total number of the states in the first set corresponding to each transmission time in the divergence phase is in an increasing trend, the total number of the states in the first set corresponding to each transmission time in the fixed phase is kept unchanged, the total number of the states in the first set corresponding to each transmission time in the combination phase is gradually reduced until the known total number of characters B and total number of bits R are reached, and the divergence phase, the fixed phase or the combination phase are only distinguished for the absolute value; the acquisition module is also used for acquiring the prior probability and the bit error probability; a processing module for transmitting V of the first set at each transmission time according to an absolute value codebookstartV of the first setendDetermining the posterior probability of the absolute value of each absolute value code word in the absolute value codebook at each transmission moment according to the prior probability acquired by the acquisition module and the bit error probability acquired by the acquisition module; a processing module further configured to transmit V 'of the second set of transmission instants according to a codebook of symbols'startV 'of the second set'endDetermining the symbol posterior probability of each symbol code word in the symbol codebook at each transmission moment according to the prior probability acquired by the acquisition module and the bit error probability acquired by the acquisition module; the processing module is further configured to determine information transmitted at the first transmission time according to a parameter estimation method, the a posteriori probability of the absolute value of each absolute value in the first transmission time absolute value codebook, and the a posteriori probability of the symbol of each symbol in the first transmission time symbol codebook.
Optionally, the processing module is specifically configured to determine a minimum number N of bits occupied by the absolute value codeword in the absolute value codebookminAnd the maximum number of bits NmaxCharacter and symbolDetermining the minimum bit number N 'of code words actually used by absolute values in the lattice structure according to the minimum bit number x and the maximum bit number t occupied by symbol code words in the code book, the total number B of characters acquired by the acquisition module and the total bit number R acquired by the acquisition module'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure BDA0001708568250000071
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure BDA0001708568250000072
r' from
Figure BDA0001708568250000073
Starting, continuously adding 1, and stopping adding 1 when R' meets the variable formula;
a processing module, specifically configured to determine a minimum bit number N'minN 'maximum number of bits'maxIntermediate variable R 'and intermediate variable l', determining second boundary time l of fixed stage and merging stage in lattice structurescAnd a maximum value q of the total number of states contained in the first setmax(ii) a Processing module, in particular for use according to qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, the processing module is specifically configured to determine that R is less than or equal to Nmin× B + t, second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
A processing module for processing the received data,in particular for determining that R is less than or equal to Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), second boundary time lscIs equal to
Figure BDA0001708568250000074
Maximum value qmaxIs equal to R-N'min×B+1；
A processing module, in particular for determining a second boundary instant l when R < RscIs equal to
Figure BDA0001708568250000075
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
A processing module, in particular for determining when R < Nmax× B + t × (B-1), second boundary time lscIs equal to
Figure BDA0001708568250000076
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
A processing module, in particular for determining that R ≧ Nmax× B + t × (B-1), second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
A processing module, in particular for determining the maximum qmaxDetermining a first boundary instant ldsIs equal to
Figure BDA0001708568250000081
The maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, the processing module is specifically configured to determine that the transmission time l is less than or equal to the first boundary time ldsWhile determining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
A processing module, specifically configured to determine that the transmission time l is greater than the first boundary time ldsAnd the transmission time l is less than or equal to the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
A processing module, specifically configured to determine that the transmission time l is greater than the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
In a third aspect, an embodiment of the present invention provides a variable length decoder, including any one of the variable length decoding apparatuses as provided in the second aspect.
The embodiment of the invention provides a variable length decoding method, which comprises the steps of transmitting the total number B of characters, transmitting the total number R of bits in a bit stream, and obtaining the minimum bit number N of absolute value code words in an absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number x and the maximum bit number t of the symbol code word in the symbol codebook and determining the boundary moment ldsAnd lscSo that it can be determined to which phase the received character belongs; and V of the first set transmitted per transmission instant according to the absolute value codebookstartV of the first setendDetermining the posterior probability of the absolute value of each absolute value code word in the absolute value codebook at each transmission moment; v 'of a second set transmitted per transmission time instant according to a codebook of symbols'startV 'of the second set'endPrior probability and bit error probability, determining a codebook of symbols at each transmission instantThe symbol posterior probability of each symbol codeword; determining information transmitted at the first transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the absolute value codebook at the first transmission moment and the symbol posterior probability of each symbol in the symbol codebook at the first transmission moment; the possible initial state of the bit stream corresponding to each character in the received bit stream can be distinguished, so that the information transmitted at each transmission moment can be known more accurately, and the problem that in the prior art, when the transmission parameter relates to the absolute value and the symbol respectively for coding, and when a transmission channel has noise interference, a variable length decoder cannot correctly identify the position of a code word corresponding to each transmission character in the bit stream, and the absolute value and the symbol correspond to different codebooks, so that an information source signal cannot be correctly recovered.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of a communication transmission system in the prior art;
FIG. 2 is a flowchart illustrating a variable length decoding method according to an embodiment of the present invention;
FIG. 3-a is a diagram illustrating a trellis representation of a variable length decoding method according to an embodiment of the present invention;
FIG. 3-b is a second schematic diagram of a trellis representation of a variable length decoding method according to an embodiment of the present invention;
FIG. 3-c is a third diagram of a trellis representation of a variable length decoding method according to an embodiment of the present invention;
FIG. 3-d is a fourth diagram illustrating a trellis representation of a variable length decoding method according to an embodiment of the present invention;
FIG. 3-e is a fifth schematic diagram of a trellis representation of a variable length decoding method according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a variable length decoding apparatus according to an embodiment of the present invention.
Reference numerals:
variable length decoding means-10;
an acquisition module-101; a processing module-102.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
For the convenience of clearly describing the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second", and the like are used for distinguishing the same items or similar items with basically the same functions and actions, and those skilled in the art can understand that the words "first", "second", and the like are not limited in number or execution order.
It should be noted that, in the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "e.g.," an embodiment of the present invention is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.
In practical applications, each transmission time l may transmit an absolute value or a symbol; considering that the absolute value is transmitted first and then the symbol is transmitted, the invention defines each transmission time l as two transmission nodes lc(i.e. |)cEqual to {1,2, …,2 × B }), wherein, the number of the odd numbers lcRepresenting the absolute value of the received character, even number lcRepresents the reception of theThe specific implementation process of the symbol of the character is as follows:
since each character contains an absolute value and a sign, we assume that the absolute value of the quantized spectral coefficient and the corresponding sign share the same transmission time l equal to {1,2,3,4}, i.e., one character is transmitted in each transmission time l; as shown in fig. 3-a to 3-e, the abscissa indicates the transmission node lcOrdinate qlcThe state of each transmission node is represented, and the number of bits occupied by the absolute value code word comprises 1,2 or 3 (namely N)min＝1、Nmax3), the number of bits occupied by the symbol codeword includes: 0. 1 or 2 (i.e. x is 0 and t is 2), when lcWhen it is odd (l)c2 × l-1), all possible states of the transmitting node constitute a first set of absolute values, when lcWhen it is even (l)c2 × l) which constitutes a second set of symbols, i.e. when l equals 1, it means that the 1 st character is transmitted, when l equals 2, it means that the 2 nd character is transmitted, when l equals 3, it means that the 3 rd character is transmitted, when l equals 4, it means that the 4 th character is transmitted, since each transmission instant l contains two transmission nodes lcThus at each transmission instant l, if the node l is transmittedcThe absolute value of the character is transmitted, then at lcThe +1 transmitting node transmits the symbol of the character.
It should be noted that each character transmitted in the bit stream does not necessarily carry a symbol, and if the transmitted character is 0, there is no symbol, that is, the absolute value of 0 is 0, and the symbol of 0 is null, and no bit needs to be transmitted; considering that the symbol is empty in the actual transmission process, namely x is equal to 0, when x is equal to 0, the character only occupies the bit number corresponding to the absolute value code word in the bit stream because the change interval of the bit number occupied by the symbol code word in the symbol codebook is [ x, t ]; therefore, in view of the general situation, the embodiment of the present invention provides a variable length decoding method, in which the variation interval of the number of bits occupied by the symbol codeword is [0, t ], that is, x is equal to 0.
In particular, from odd numbers lc(absolute value) to even number lc(symbols), state changes in lattice structureMay range from x to t (where x equals 0); in contrast, from even number lc(symbols) to odd numbers lc(Absolute value), the state variation range in the lattice structure can be N'minTo N'max(ii) a Illustratively, when l is equal to 1 as shown in FIG. 3-a, it includes: lcIs equal to 1 and lcEqual to 2 two transmission nodes; where l equals 1 indicates that the first character is transmitted, lcEqual to 1 indicates that the absolute value of the first character has been transmitted, lcEqual to 2 denotes that the symbol of the first character is transmitted, and the meaning of each transmission node in l equal to 2, l equal to 3 and l equal to 4 is the same as that of each transmission node in l equal to 1, and will not be described herein again.
In particular, consider the first sign and then the absolute value (i.e., the odd number l)cThe symbol, even l, representing the received charactercRepresenting the absolute value of the character received), and the absolute value passed first and then the symbol (i.e., the odd number l)cRepresenting the absolute value of the received character, even number lcThe symbol representing the character received) is similar and will not be described in detail herein.
Example one
An embodiment of the present invention provides a variable length decoding method, as shown in fig. 2, including:
s101, acquiring the total number B and the total bit number R of characters transmitted in a bit stream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0.
It should be noted that, in practical applications, as shown in fig. 1, a source encoder converts a source signal into a bit stream represented by 0 or 1 according to an absolute value codebook and a symbol codebook.
Illustratively, assuming that the source signal needs to transmit 4 characters of +5, -6, +1.2, and 0, respectively, the absolute value of +5 corresponds to the absolute valueThe code word in the value codebook is y(0)The absolute value of (1,0,1) to (6) corresponds to the codeword y in the absolute value codebook(1)The absolute value of +1.2 corresponds to the codeword y in the absolute value codebook(2)That is (1,1), an absolute value of 0 corresponds to a codeword y in an absolute value codebook(3)When the symbol code word of the symbol codebook is H, the "+" sign corresponds to (1,0,0)(0)When the symbol code word of the "-" sign-corresponding symbol codebook is H, (0) is(1)When the sign bit is not present, the sign code word of the sign codebook is H (0,1)(2)() is used. (it should be noted that, when the transmitted character is 0, since the absolute value of the character 0 is 0 and 0 itself has no sign, that is, the bit number of the sign of 0 is 0,0 does not occupy the bit number of the sign in the actual transmission process).
After converting +5, -6, +1.2, and 0 into a bitstream, the corresponding bitstream can be expressed as: 1010001110100 (total number of transmitted characters B equals 4, total number of bits R equals 13); when the bit stream is transmitted in a transmission channel, and a decoding device receives the bit stream, it is necessary to know the corresponding start position and end position of each character in the bit stream at any transmission time to recover the corresponding information.
S102, according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by the symbol code word in the symbol codebook, the total number B of characters and the total bit number R are determined, and the first boundary time l of a divergent stage and a fixed stage in the lattice structure is determineddsSecond boundary time l of the fixed phase and the merging phasesc。
Optionally, in the variable length decoding method provided in the embodiment of the present invention, the minimum number N of bits occupied by the absolute value codeword in the absolute value codebook is used as a referenceminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by the symbol code word in the symbol codebook, the total number B of characters and the total bit number R are determined, and the first boundary time l of a divergent stage and a fixed stage in the lattice structure is determineddsSecond boundary time l of the fixed phase and the merging phasescThe method comprises the following steps:
S1020according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number N 'of code words actually used by absolute values in the trellis structure according to the minimum bit number x and the maximum bit number t occupied by symbol code words in the symbol codebook, the total number B of characters and the total bit number R'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure BDA0001708568250000121
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure BDA0001708568250000131
r' from
Figure BDA0001708568250000132
And starting to continuously add 1, and stopping adding 1 when R' meets the variable formula.
S1021, according to the determined minimum bit number N'minN 'maximum number of bits'maxIntermediate variable R 'and intermediate variable l', determining second boundary time l of fixed stage and merging stage in lattice structurescAnd a maximum value q of the total number of states contained in the first setmax。
S1022, according to qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, in the variable length decoding method provided in the embodiment of the present invention, S1021 includes: according to the determined minimum bit number N'minN 'maximum number of bits'maxIntermediate variables R 'and l' to determine the second boundary time l of the fixed phase and the merging phasescAnd a maximum value q of the total number of states contained in the first setmaxThe method comprises the following steps:
s1021-1, when R is determined to be less than or equal to Nmin× B + t, second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
S1021-2, when R is determined to be less than or equal to Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), second boundary time lscIs equal to
Figure BDA0001708568250000133
Maximum value qmaxIs equal to R-N'min×B+1；
S1021-3, when R < R' is determined, the second boundary time lscIs equal to
Figure BDA0001708568250000134
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
S1021-4, when R < N is determinedmax× B + t × (B-1), second boundary time lscIs equal to
Figure BDA0001708568250000135
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
S1021-5, when R is determined to be more than or equal to Nmax× B + t × (B-1), second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
S1022, according to qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+ t, comprising:
s1022-1, according to the maximum value qmaxDetermining a first boundary instant ldsIs equal to
Figure BDA0001708568250000141
The maximum value of the total number of states contained in the second set is equal to qmax+t。
S103, according to the first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set of the first transmission time is VstartThe maximum value of the first set of the ith transmission time is VendAnd the minimum value of the second set of the l transmission time instants is V'startThe maximum value of the second set of the l transmission time instants is V'end(ii) a The first set comprises at least one possible state, the state in the first set refers to the total number of bits of which the absolute value is transmitted to the current transmission time, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of which the symbols are transmitted to the current transmission time, the total number of the states in the first set corresponding to each transmission time in the divergence phase is in an increasing trend, the total number of the states in the first set corresponding to each transmission time in the fixed phase is kept unchanged, the total number of the states in the first set corresponding to each transmission time in the combination phase is gradually reduced until the known total number of characters B and total number of bits R are reached, and the divergence phase, the fixed phase or the combination phase are only distinguished according to the absolute value.
Specifically, in practical applications, according to the conventional lattice representation, the present application proposes a new lattice representation, which can have VLCs of different codebooks for absolute value and sign.
Illustratively, 4 characters are transmitted with t-2, and the absolute value of each character in the absolute value codebook is represented as y(0)＝(1,0,1)，y(1)＝(0)，y(2)＝(1,1)，y(3)That is, (1,0,0), the symbol of each character in the symbol codebook is represented as H(0)＝(0)，H(1)＝(0,1)，H(2)Description is given for an example; the number of bits occupied by the absolute value code word includes three types, namely 1,2 or 3, and the number of bits occupied by the symbol code word includes: 0. 1 or 2, as shown in FIG. 3-aThe table of 5 different total bits R (R6, R10, R13, R17 and R18) is shown in fig. 3-e.
Specifically, in practical applications, we find that the minimum number of bits N occupied by the absolute value codeword in the absolute value codebookminAnd the maximum number of bits NmaxMinimum bit number x and maximum bit number t occupied by symbol codewords in the symbol codebook, total number B of characters, total bit number R, and minimum bit number N 'of absolute value codewords actually used for absolute values in the trellis structure'minAnd the maximum bit number N 'of the absolute value code word actually used by the absolute value in the trellis structure'maxThe following relationships exist:
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
wherein N isminAnd NmaxRespectively represents the minimum value of all the code words in the codebook (N in this example)min1) and maximum value (N in this example)max＝3)。
Correspondingly, for each transmission time, the divergence phase, the fixed phase and the combination phase are only based on the odd number of transmission nodes lcCorresponding number of states, irrespective of even number of transmitting nodes lcThe corresponding number of states. That is, the first boundary time lds(divergent and stationary phase) and a second boundary instant lsc(stationary phase and combining phase) with respect to the transmission time instant l (instead of the transmission node l)c)。
For example, as shown in fig. 3-b, the total number of bits to be transmitted is illustrated as R ═ 10, and the specific implementation process is as follows:
when l is equal to 1 and lcWhen the absolute value is equal to 1, transmitting the absolute value of the first character, wherein the bit number occupied by the possibly transmitted absolute value code word comprises 1,2 or 3; by the current transmission node lcEqual to 1, the total number of bits transmitted in the bitstream may be 1,2 or 3; thus, lcEqual to 1, the absolute value corresponds to a first set of states of {1,2,3}, i.e., V of the first setstartIs 1, V of the first setendIs 3.
When l is equal to 1 and lcWhen the number is equal to 2, transmitting the symbol of the first character, wherein the number of bits occupied by the possibly transmitted symbol code word comprises 0,1 or 2; by the current transmission node lcEqual to 2, the total number of bits transmitted in the bitstream may be 1,2,3,4, or 5; thus, lcEqual to 2, the second set of symbol corresponding states is {1,2,3,4,5}, i.e., V 'of the second set'startIs 1, V of the second set'endIs 5.
When l is equal to 2 and lcWhen the absolute value is equal to 3, transmitting the absolute value of the second character, wherein the bit number occupied by the possibly transmitted absolute value code word comprises 1,2 or 3; by the current transmission node lcEqual to 3, the total number of bits transmitted in the bitstream may be 2,3,4,5,6,7, or 8; thus, lcEqual to 3, the absolute value corresponds to a first set of states of {2,3,4,5,6,7,8}, i.e., V of the first setstartIs 2, V of the first setendIs 8.
When l is equal to 2 and lcWhen the number is equal to 4, transmitting the symbol of the second character, wherein the number of bits occupied by the possibly transmitted symbol code word comprises 0,1 or 2; by the current transmission node lcEqual to 4, the total number of bits transmitted in the bitstream may be 2,3,4,5,6,7, or 8; thus, lcEqual to 4, the second set of symbol corresponding states is {2,3,4,5,6,7,8}, i.e., V 'of the second set'startIs 2, V of the second set'endIs 8.
When l is equal to 3 and lcWhen the absolute value is equal to 5, transmitting the absolute value of the third character, wherein the bit number occupied by the possibly transmitted absolute value code word comprises 1,2 or 3; by the current transmission node lcEqual to 5, the total number of bits transmitted in the bitstream may be 3,4,5,6,7,8, or 9; thus, lcEqual to 5, the absolute value corresponds to a first set of states of {3,4,5,6,7,8,9}, i.e., V of the first setstartV of the first set being 3endIs 9.
When l is equal to 3 and lcEqual to 6, the symbol of the third character is transmitted, possiblyThe number of bits occupied by the symbol codeword of (1) includes 0,1 or 2; by the current transmission node lcEqual to 6, the total number of bits transmitted in the bitstream may be 5,6,7,8 or 9; thus, lcEqual to 6, the second set of symbol corresponding states is {5,6,7,8,9}, i.e., V 'of the second set'startIs 5, V of the second set'endIs 9.
When l is equal to 4 and lcWhen the absolute value is equal to 7, transmitting the absolute value of the fourth character, wherein the bit number occupied by the possibly transmitted absolute value code word comprises 1,2 or 3; by the current transmission node lcEqual to 7, the total number of bits transmitted in the bitstream may be 8,9 or 10; thus, lcEqual to 7, the absolute value corresponds to a first set of states of 8,9,10, i.e. V of the first setstartV of the first set being 8endIs 10.
When l is equal to 4 and lcWhen the number equals 8, transmitting the symbol of the fourth character, wherein the number of bits occupied by the possibly transmitted symbol code word comprises 0,1 or 2; by the current transmission node lcEqual to 8, the total number of bits transmitted in the bitstream may be 10; thus, lcAt 8, the second set of symbol corresponding states is {10}, i.e., V 'of the second set'startIs 10, V of the second set'endIs 10.
As can be seen from the above, lcThe first set of states corresponding to absolute values equal to 1 is {1,2,3}, lcThe first set of states corresponding to absolute values equal to 3 is {2,3,4,5,6,7,8}, lcThe first set of states corresponding to an absolute value equal to 5 is {3,4,5,6,7,8,9}, lcA first set of states corresponding to absolute values equal to 7 is {8,9,10 }; thus, lcThe number of states contained in the first set is 3, l when 1 is equalcThe number of states contained in the first set equal to 3 is 7, lcThe number of states contained in the first set equal to 5 is 7, lcThe number of states contained in the first set equal to 7 is 3; due to the fact thatcIs equal to 1 to lcThe number of states contained in the first set, equal to 3, of each transmission node increases progressively, so thatcIs equal to 1, lcIs equal to 2 and lcIs equal to3 in the divergence phase; due to the fact thatcIs equal to 3 to lcThe number of states contained in the first set equal to 5 per transmission node remains unchanged, so lcIs equal to 3, lcIs equal to 4 and lcEqual to 5 in the stationary phase; due to the fact thatcIs equal to 5 to lcThe number of states contained in the first set, equal to 7, of each transmission node is progressively reduced, so thatcIs equal to 5, lcIs equal to 6 and lcEqual to 7 in the merge phase; due to the fact thatcIs equal to 1, lcIs equal to 3, lcEqual to 5 and lcThe maximum number of states contained in the first set equal to each transmission node in 7 is 7, so q ismaxEqual to 7.
It should be noted that in practical applications, as shown in FIG. 3-a, the cut-off is lcThe maximum number of bits transmitted in the bitstream equals 5 hours is 9 and the total number of transmitted bits is R10, i.e. cut off to lcThe total number of bits transmitted in the bitstream equal to 8 is 10; consider the equation fromcIs equal to 5 to lcEqual to 7 each transmission node should have at least 1 bit transmission and therefore, cut to lcEqual to 5, the total number of bits transmitted in the bitstream cannot be greater than 9; also for example, by lcEqual to 7, the maximum value of the total number of bits transmitted in the bitstream is 10, and the total number of transmitted bits is R-10, i.e. cut off to lcThe total number of bits transmitted in the bitstream equal to 8 is 10; consider the equation fromcIs equal to 7 to lcEqual to 8 transmission nodes can transmit without bits; thus, cut off tocThe total number of bits transmitted in the bit stream equal to 7 may be 10.
In particular, since the maximum value of the total number of states contained in the second set is equal to qmax+ t, whereas in the above embodiment t is equal to 2, so that the maximum value of the total number of states contained in the second set is equal to qmax+2。
In particular, V of the first set of R-6 or R-13 or R-17 or R-18startV of the first setendV 'of the second set'startV 'of the second set'end、qmaxThe determination process of the divergent phase, the fixed phase and the merge phase is similar to that of R10, and is not described herein again.
Optionally, in the variable length decoding method provided in the embodiment of the present invention, the first boundary time l is used as a referencedsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission time and a second set of states corresponding to the symbols, including:
s1030, when the transmission time l is determined to be less than or equal to the first boundary time ldsWhile determining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
S1031, when the transmission time l is determined to be larger than the first boundary time ldsAnd the transmission time l is less than or equal to the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
S1032, when the transmission time l is determined to be larger than the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min× l, (B-l +1) - × (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
And S104, acquiring the prior probability and the bit error probability.
It should be noted that the calculation method of the prior probability and the bit error probability is similar to that of the prior art, and is not described herein again.
S105, V of the first set transmitted at each transmission moment according to the absolute value codebookstartV of the first setendA prior probability and a bit error probability, determining the absolute value posterior probability of each absolute value codeword in the absolute value codebook at each transmission moment.
S106, V 'of a second set transmitted according to a symbol codebook and each transmission time'startV 'of the second set'endA prior probability and a bit error probability, determining a symbol posterior probability for each symbol codeword in the symbol codebook at each transmission instant.
S107, determining the information transmitted at the l transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the l transmission moment absolute value codebook and the symbol posterior probability of each symbol in the l transmission moment symbol codebook.
The embodiment of the invention provides a variable length decoding method, which comprises the steps of transmitting the total number B of characters, transmitting the total number R of bits in a bit stream, and obtaining the minimum bit number N of absolute value code words in an absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number x and the maximum bit number t of the symbol code word in the symbol codebook and determining the boundary moment ldsAnd lscSo that it can be determined to which phase the received character belongs; and V of the first set transmitted per transmission instant according to the absolute value codebookstartV of the first setendDetermining the posterior probability of the absolute value of each absolute value code word in the absolute value codebook at each transmission moment; v 'of a second set transmitted per transmission time instant according to a codebook of symbols'startV 'of the second set'endDetermining the symbol posterior probability of each symbol code word in the symbol codebook at each transmission moment; determining information transmitted at the first transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the absolute value codebook at the first transmission moment and the symbol posterior probability of each symbol in the symbol codebook at the first transmission moment; since it is possible to distinguish the bit stream corresponding to each character in the received bit streamThe initial state, therefore, the information transmitted at each transmission moment can be known more accurately, and the problem that in the prior art, when the transmission parameters relate to absolute values and symbols for encoding respectively at the same time, and when a transmission channel has noise interference, a variable length decoder cannot correctly identify the position of a code word corresponding to each transmission character in a bit stream, and different codebooks are corresponding to the absolute values and the symbols, so that an information source signal cannot be correctly recovered.
Example two
An embodiment of the present invention provides a variable length decoding apparatus 10, as shown in fig. 4, including:
an obtaining module 101, configured to obtain a total number B and a total number R of characters transmitted in a bitstream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0.
A processing module 102, configured to determine a minimum number N of bits occupied by an absolute value codeword in an absolute value codebookminAnd the maximum number of bits NmaxDetermining a minimum bit number x and a maximum bit number t occupied by a symbol codeword in a symbol codebook, a total number B of characters acquired by an acquisition module 101 and a total bit number R acquired by the acquisition module 101, and determining a first boundary time l of a divergent stage and a fixed stage in a trellis structuredsSecond boundary time l of the fixed phase and the merging phasesc。
The processing module 102 is further configured to determine a first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set of the first transmission time is VstartThe maximum value of the first set of the ith transmission time is VendAnd the minimum value of the second set of the l transmission time instants is V'startThe maximum value of the second set of the l transmission time instants is V'end(ii) a The first set comprises at least one possible state, the state in the first set refers to the total number of bits of which the absolute value is transmitted to the current transmission time, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of which the symbols are transmitted to the current transmission time, the total number of the states in the first set corresponding to each transmission time in the divergence phase is in an increasing trend, the total number of the states in the first set corresponding to each transmission time in the fixed phase is kept unchanged, the total number of the states in the first set corresponding to each transmission time in the combination phase is gradually reduced until the known total number of characters B and total number of bits R are reached, and the divergence phase, the fixed phase or the combination phase are only distinguished according to the absolute value.
The obtaining module 101 is further configured to obtain the prior probability and the bit error probability.
The processing module 102 is further configured to transmit the first set of V per transmission time according to an absolute value codebookstartV of the first setendThe prior probability acquired by the acquisition module 101 and the bit error probability acquired by the acquisition module 101 determine the absolute value posterior probability of each absolute value codeword in the absolute value codebook at each transmission moment.
Processing module 102 further configured to transmit V 'of the second set of transmission time instants according to a codebook of symbols'startV 'of the second set'endThe prior probability acquired by the acquisition module 101 and the bit error probability acquired by the acquisition module 101 determine the symbol posterior probability of each symbol codeword in the symbol codebook at each transmission moment.
The processing module 102 is further configured to determine information transmitted at the ith transmission time according to a parameter estimation method, the a posteriori probability of the absolute value of each absolute value in the ith transmission time absolute value codebook, and the a posteriori probability of each symbol in the ith transmission time symbol codebook.
Optionally, the processing module 102 is specifically configured to determine a minimum number N of bits occupied by the absolute value codeword in the absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number N 'of a code word actually used by an absolute value in a trellis structure according to the minimum bit number x and the maximum bit number t occupied by a symbol code word in a symbol codebook, the total number B of characters acquired by the acquisition module 101 and the total bit number R acquired by the acquisition module 101'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure BDA0001708568250000201
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure BDA0001708568250000202
r' from
Figure BDA0001708568250000211
Starting, continuously adding 1, and stopping adding 1 when R' meets the variable formula;
the processing module 102 is specifically configured to determine a minimum bit number N'minN 'maximum number of bits'maxIntermediate variable R 'and intermediate variable l', determining second boundary time l of fixed stage and merging stage in lattice structurescAnd a maximum value q of the total number of states contained in the first setmax。
A processing module 102, in particular for determining the qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, the processing module 102 is specifically configured to determine that R ≦ Nmin× B + t, second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
Processing module 102, specifically for when it is determined that R ≦ Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), second boundary time lscIs equal to
Figure BDA0001708568250000212
Maximum value qmaxIs equal to R-N'min×B+1；
A processing module 102, specifically configured to determine a second boundary instant l when R < R ″scIs equal to
Figure BDA0001708568250000213
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
A processing module 102, in particular for determining when R < Nmax× B + t × (B-1), second boundary time lscIs equal to
Figure BDA0001708568250000214
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
Processing Module 102, in particular for when it is determined that R ≧ Nmax× B + t × (B-1), second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
A processing module 102, in particular for determining a maximum qmaxDetermining a first boundary instant ldsIs equal to
Figure BDA0001708568250000215
The maximum value of the total number of states contained in the second set is equal to qmax+t。
Optionally, the processing module 102 is specifically configured to determine that the transmission time l is less than or equal to the first boundary time ldsWhile determining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max×(B-l)-t×(B-l))，V of a second set'endIs equal to min (V)end+t,R-N'min×(B-l))；
The processing module 102 is specifically configured to determine that the transmission time l is greater than the first boundary time ldsAnd the transmission time l is less than or equal to the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), a second set of V'endIs equal to min (V)end+t,R-N'min×(B-l))；
The processing module 102 is specifically configured to determine that the transmission time l is greater than the second boundary time lscWhile determining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
The embodiment of the invention provides a variable length decoding device, which is characterized in that the minimum bit number N of absolute value code words in an absolute value codebook is determined by the total number B of transmission characters, the total number R of bits in a bit stream and the total number of bits in the absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number x and the maximum bit number t of the symbol code word in the symbol codebook and determining the boundary moment ldsAnd lscSo that it can be determined to which phase the received character belongs; and V of the first set transmitted per transmission instant according to the absolute value codebookstartV of the first setendDetermining the posterior probability of the absolute value of each absolute value code word in the absolute value codebook at each transmission moment; v 'of a second set transmitted per transmission time instant according to a codebook of symbols'startV 'of the second set'endDetermining the symbol posterior probability of each symbol code word in the symbol codebook at each transmission moment; root of herbaceous plantDetermining information transmitted at the first transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the absolute value codebook at the first transmission moment and the symbol posterior probability of each symbol in the symbol codebook at the first transmission moment; the possible initial state of the bit stream corresponding to each character in the received bit stream can be distinguished, so that the information transmitted at each transmission moment can be known more accurately, and the problem that in the prior art, when the transmission parameter relates to the absolute value and the symbol respectively for coding, and when a transmission channel has noise interference, a variable length decoder cannot correctly identify the position of a code word corresponding to each transmission character in the bit stream, and the absolute value and the symbol correspond to different codebooks, so that an information source signal cannot be correctly recovered.
EXAMPLE III
An embodiment of the present invention provides a variable length decoder, including any one of the variable length decoding apparatuses 10 as provided in embodiment two. For a specific variable length decoding apparatus 10, reference may be made to the related description in the second embodiment of the apparatus, and details are not repeated here.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (9)

1. A variable length decoding method, comprising:
acquiring the total number B and the total bit number R of characters transmitted in a bit stream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0;
according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxDetermining the minimum bit number x and the maximum bit number t occupied by the symbol code words in the symbol codebook, the total number B of the characters and the total bit number R, and determining the first boundary time l of a divergent stage and a fixed stage in the lattice structuredsSecond boundary time l of the fixed phase and the merging phasesc；
According to the first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set at the ith transmission time is VstartThe maximum value of the first set at the ith transmission moment is VendThe minimum value of the second set at the l transmission time is V'startWherein the maximum value of the second set at the l transmission time instant is V'end(ii) a Wherein the first set comprises at least one possible state, the state in the first set is the total number of bits until the absolute value is transmitted to the current transmission moment, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of symbols transmitted by the current transmission time, the total number of states contained in the first set corresponding to each transmission time in the divergent phase is in an increasing trend, the total number of states contained in the first set corresponding to each transmission time in the fixed phase is kept unchanged, the total number of states contained in the first set corresponding to each transmission time in the combined phase is gradually reduced until a known total number of characters B and a known total number of bits R are reached, and the divergent phase, the fixed phase or the combined phase is only distinguished according to absolute values;
acquiring prior probability and bit error probability;
v of the first set transmitted per the transmission instant according to the absolute value codebookstartV of the first setendSaid first stepDetermining an absolute value posterior probability of each absolute value codeword in the absolute value codebook at each of the transmission moments;
v 'of the second set transmitted according to the symbol codebook for each of the transmission time instants'startV of the second set'endDetermining a symbol posterior probability of each symbol codeword in the symbol codebook at each of the transmission moments, the prior probability and the bit error probability;
and determining the information transmitted at the ith transmission moment according to a parameter estimation method, the absolute value posterior probability of each absolute value in the absolute value codebook at the ith transmission moment and the symbol posterior probability of each symbol in the symbol codebook at the ith transmission moment.
2. The method of claim 1, wherein said minimum number of bits N occupied by absolute value codewords in said absolute value codebook is determined according to the absolute value of said codewordminAnd the maximum number of bits NmaxDetermining the minimum bit number x and the maximum bit number t occupied by the symbol code words in the symbol codebook, the total number B of the characters and the total bit number R, and determining the first boundary time l of a divergent stage and a fixed stage in the lattice structuredsSecond boundary time l of the fixed phase and the merging phasescThe method comprises the following steps:
according to the minimum bit number N occupied by the absolute value code word in the absolute value codebookminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by symbol code words in the symbol codebook, the total number B of the characters and the total bit number R determine the minimum bit number N 'of code words actually used by absolute values in the trellis structure'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure FDA0001708568240000021
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure FDA0001708568240000022
said R' is selected from
Figure FDA0001708568240000023
Starting to continuously add 1, and stopping adding 1 when the R' meets the variable formula;
according to the determined minimum bit number N'minN 'of the maximum bit number'maxDetermining a second boundary time l of a fixed stage and a merging stage in the lattice structure according to the intermediate variable R' and the intermediate variable lscAnd a maximum value q of the total number of states contained in said first setmax；
According to said qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in said second set is equal to qmax+t。
3. The variable length decoding method of claim 2, wherein the variable length is according to the determined minimum number of bits N'minN 'of the maximum bit number'maxThe intermediate variable R 'and the intermediate variable l' determine a second boundary time l of the fixed phase and the merging phasescAnd a maximum value q of the total number of states contained in said first setmaxThe method comprises the following steps:
when it is determined that R is not more than Nmin× B + t, the second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
When it is determined that R is not more than Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), the second boundary time lscIs equal to
Figure FDA0001708568240000031
Maximum value qmaxIs equal to R-N'min×B+1；
The second boundary instant/when it is determined that R < RscIs equal to
Figure FDA0001708568240000032
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
When it is determined that R < Nmax× B + t × (B-1), the second boundary time lscIs equal to
Figure FDA0001708568240000033
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
When it is determined that R.gtoreq.Nmax× B + t × (B-1), the second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
According to said qmaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in said second set is equal to qmax+ t, comprising:
according to said maximum value qmaxDetermining said first boundary instant ldsIs equal to
Figure FDA0001708568240000034
The maximum value of the total number of states contained in said second set is equal to qmax+t。
4. A variable length decoding method according to claim 2, wherein said first boundary time i is used as a function of said first boundary timedsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission time and a second set of states corresponding to the symbols, including:
when it is determined that the transmission time/is less than or equal to the first boundary time/dsDetermining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), V 'of the second set'endIs equal to min (V)end+t,R-N'min×(B-l))；
When it is determined that the transmission time/is greater than the first boundary time/dsAnd the transmission time l is less than or equal to the second boundary time lscDetermining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), V 'of the second set'endIs equal to min (V)end+t,R-N'min×(B-l))；
When it is determined that the transmission time l is greater than the second boundary time lscDetermining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
5. A variable length decoding apparatus, comprising:
the acquisition module is used for acquiring the total number B and the total bit number R of the characters transmitted in the bit stream; each character comprises an absolute value and a symbol, each absolute value and each symbol are respectively and independently transmitted and are coded by different codebooks, each absolute value corresponds to an absolute value code word in an absolute value codebook, each symbol corresponds to a symbol code word in a symbol codebook, the absolute value codebook adopts a variable length coding mode, and the symbol codebook adopts a variable length coding mode; wherein B is an integer greater than 0, and R is an integer greater than 0;
a processing module, configured to determine a minimum number of bits N occupied by the absolute value codeword in the absolute value codebookminAnd the maximum number of bits NmaxDetermining a minimum bit number x and a maximum bit number t occupied by a symbol codeword in the symbol codebook, a total number B of the characters acquired by the acquisition module and a total bit number R acquired by the acquisition module, and determining a first boundary time l of a divergent stage and a fixed stage in a lattice structuredsSecond boundary time l of the fixed phase and the merging phasesc；
The processing module is further configured to determine a first boundary time ldsAnd a second boundary instant lscDetermining a first set of states corresponding to the absolute value of the ith transmission moment and a second set of states corresponding to the symbols; wherein the minimum value of the first set at the ith transmission time is VstartThe maximum value of the first set at the ith transmission moment is VendThe minimum value of the second set at the l transmission time is V'startWherein the maximum value of the second set at the l transmission time instant is V'end(ii) a Wherein the first set comprises at least one possible state, the state in the first set is the total number of bits until the absolute value is transmitted to the current transmission moment, the second set comprises at least one possible state, the state in the second set refers to the total number of bits of symbols transmitted by the current transmission time, the total number of states contained in the first set corresponding to each transmission time in the divergent phase is in an increasing trend, the total number of states contained in the first set corresponding to each transmission time in the fixed phase is kept unchanged, the total number of states contained in the first set corresponding to each transmission time in the combined phase is gradually reduced until a known total number of characters B and a known total number of bits R are reached, and the divergent phase, the fixed phase or the combined phase is only distinguished according to absolute values;
the acquisition module is further used for acquiring a prior probability and a bit error probability;
the processing module is further configured to transmit the V of the first set for each transmission time according to the absolute value codebookstartV of the first setendDetermining the prior probability of each absolute value codeword in the absolute value codebook at each transmission moment according to the prior probability acquired by the acquisition module and the bit error probability acquired by the acquisition module;
the processing module is further configured to transmit the second set of V 'according to the symbol codebook for each of the transmission time instants'startV of the second set'endDetermining a symbol posterior probability of each symbol codeword in the symbol codebook at each transmission moment according to the prior probability acquired by the acquisition module and the bit error probability acquired by the acquisition module;
the processing module is further configured to determine information transmitted at the ith transmission time according to a parameter estimation method, the absolute value posterior probability of each absolute value in the absolute value codebook at the ith transmission time, and the symbol posterior probability of each symbol in the symbol codebook at the ith transmission time.
6. The variable length decoding device according to claim 5, wherein the processing module is specifically configured to determine the minimum number of bits N occupied by the absolute value codeword in the absolute value codebook according to the minimum number of bits N occupied by the absolute value codewordminAnd the maximum number of bits NmaxThe minimum bit number x and the maximum bit number t occupied by symbol code words in the symbol codebook, the total number B of the characters acquired by the acquisition module and the total bit number R acquired by the acquisition module determine the minimum bit number N 'of code words actually used by absolute values in the trellis structure'minAnd the maximum bit number N 'of code words actually used by absolute values in the trellis structure'maxIntermediate variable R 'and intermediate variable l'; wherein,
N'min＝max(R-Nmax×(B-1)-t×B,Nmin)；
N'max＝min(R-Nmin×(B-1),Nmax)；
Figure FDA0001708568240000051
wherein R 'is the smallest integer value of R' that satisfies the variable formula:
Figure FDA0001708568240000052
said R' is selected from
Figure FDA0001708568240000061
Starting to continuously add 1, and stopping adding 1 when the R' meets the variable formula;
the processing module is specifically configured to determine the minimum bit number N'minN 'of the maximum bit number'maxDetermining a second boundary time l of a fixed stage and a merging stage in the lattice structure according to the intermediate variable R' and the intermediate variable lscAnd a maximum value q of the total number of states contained in said first setmax；
The processing module is specifically configured to determine q from themaxDetermining the first boundary time l of the divergent stage and the fixed stage in the lattice structuredsAnd the maximum value of the total number of states contained in said second set is equal to qmax+t。
7. The variable length decoding apparatus according to claim 6, wherein the processing module is specifically configured to determine that R ≦ Nmin× B + t, the second boundary time lscEqual to B, maximum value qmaxIs equal to R-N'min×B+1；
The processing module is specifically used for determining that R is less than or equal to Nmax×(B-l')+Nmin× l '+ t × (B-l' +1), the second boundary time lscIs equal to
Figure FDA0001708568240000062
Maximum value qmaxIs equal to R-N'min×B+1；
The processing module is specifically configured to determine that R < R', the second boundary time lscIs equal to
Figure FDA0001708568240000063
Maximum value qmaxIs equal to (N'max-N'min+t)×(B-lsc)+t+1；
The processing module is specifically used for determining that R is less than Nmax× B + t × (B-1), the second boundary time lscIs equal to
Figure FDA0001708568240000064
Maximum value qmaxIs equal to (N'max+t)×B-R+1；
The processing module is specifically used for determining that R is more than or equal to Nmax× B + t × (B-1), the second boundary time lscEqual to B, maximum value qmaxIs equal to (N'max+t)×B-R+1；
The processing module is specifically configured to determine the maximum value qmaxDetermining said first boundary instant ldsIs equal to
Figure FDA0001708568240000065
The maximum value of the total number of states contained in said second set is equal to qmax+t。
8. The variable length decoding device according to claim 6, wherein the processing module is specifically configured to determine that the transmission time/is less than or equal to the first boundary time/dsDetermining V of the first setstartIs equal to N'min× l, V of the first setendIs equal to N'max× l + t × (l-1), V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), V 'of the second set'endIs equal to min (V)end+t,R-N'min×(B-l))；
The processing module is particularly adapted to determine the transmissionThe time l is greater than the first boundary time ldsAnd the transmission time l is less than or equal to the second boundary time lscDetermining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to Vstart+qmax-1, V 'of the second set'startIs equal to max (V)start,R-N'max× (B-l) -t × (B-l)), V 'of the second set'endIs equal to min (V)end+t,R-N'min×(B-l))；
The processing module is specifically configured to determine that the transmission time l is greater than the second boundary time lscDetermining V of the first setstartIs equal to max (N'min×l,R-t×(B-l+1)-N'max× (B-l)), V of the first setendIs equal to R-N'min× (B-l), V 'of the second set'startIs equal to min (V)start+t,R-t×(B-l)-N'max× (B-l)), V 'of the second set'endIs equal to R-N'min×(B-l)。
9. A variable length decoder comprising the variable length decoding apparatus according to any one of claims 5 to 8.
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